As is known, the essential condition for straightening repairs to damaged vehicle body bodyworks and chassis so as to carry out continuous monitoring during straightening on a bench ramp is that the vehicle is disposed on the bench ramp in a precise position defined by the lower plane of the vehicle that must be parallel to the upper support plane of the bench ramp prior to being secured thereon and the median longitudinal axis of the vehicle must coincide with the longitudinal axis of the bench ramp. If these two conditions are not met, the monitoring measurements would be inaccurate as a result of which the straightening repairs would not be carried out correctly since there would be no accurate reference points.
In order to place a damaged vehicle on a bench ramp an elevator bridge or a similar device is used which is able to lift and support the whole weight of the damaged vehicle as it supplies it above the bench ramp. In any case, as this preliminary positioning is carried out without any positional accuracy of the vehicle with respect to the bench ramp, steps must be taken thereafter to achieve the accurate relationship of superimposition until both of the above-mentioned conditions are met, after which the damaged vehicle maybe secured to the bench ramp.
In order to satisfy the above requirements bench ramps are known which are simple measuring bridges and are structured substantially to comprise a rectangular frame on which positionally adjustable means mounted and can be moved in each of three directions perpendicular to one another. These movable means is essentially slide means mounted to slide on two longitudinal beams with slide guides of the rectangular frame which in turn support transverse beams located at right angles to the first beams and on which further slide means which in turn support vertically telescopic means are mounted so that they can be slidably positioned in a similar manner. These latter vertically telescopic means are adapted to be connected in a fixed manner to points of the undamaged bodywork at the sides of the damaged portion to be straightened while the latter is successively subjected to straightening forces by chain means appropriately anchored thereto and stressed in a tensile manner. This bench ramp structure is also provided with millimetric rods for detecting the position to be imposed on the respective slide and telescopic means and with means for locking the latter in their respective positions. These latter locking mean are of the type comprising, for instance, toothed rack-type members and respective members engaging with the toothed members with corresponding locking members having clamps.
Bearing in mind that the bodyworks of vehicles tend to have increasingly curved profiles and that in order to avoid collateral component forces resulting from the straightening action on the damaged portion as is normally the case with the bench ramp structures known at present, it has been observed in practice that in order to carry out an ever more sophisticated straightening operation on the damaged portions of bodyworks it is advantageous to connect both the telescopic anchoring means at the sides of the damaged portion and the tensioning chain means in the damaged portion in a manner which is as perpendicular as possible to the respective anchoring points. Attempts to utilize such a structure have not led however to desirable results.